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Date:      Mon, 16 Sep 2024 17:45:44 -0400
From:      Chris Ross <cross+freebsd@distal.com>
To:        freebsd-net@freebsd.org, Roy Marples <roy@marples.name>
Subject:   Re: IPv6 neighbor flaps for ISP router are occurring frequently
Message-ID:  <83BCC913-3375-4847-B720-5F06D76F6646@distal.com>
In-Reply-To: <89F4F5A4-E3D9-4A43-84F6-908E3FA221A6@distal.com>
References:  <89F4F5A4-E3D9-4A43-84F6-908E3FA221A6@distal.com>

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Apologies for lack of important context, the below discusses a FreeBSD
14.1 amd64 system.

Thank you.

> On Sep 16, 2024, at 16:05, Chris Ross <cross+freebsd@distal.com> =
wrote:
>=20
> Hello.  Following the earlier thread "DHCPv6 IA_PD - how-to=E2=80=9D I =
have been
> bringing up a new gateway router for my network.  With Roy=E2=80=99s =
help, I
> have IPv6 working as expected, but I am seeing something that I =
suspect
> is unusual.  Roy doesn=E2=80=99t think it=E2=80=99s specific to =
dhcpcd, as it is caused
> by routing changes that dhcpcd is merely reacting to.
>=20
> While dhcpcd is running, it repeatedly logs the following to =
daemon.log:
>=20
> Sep 16 15:55:53 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce =
is unreachable
> Sep 16 15:55:54 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce =
is reachable again
> Sep 16 15:55:54 logrus dhcpcd[50070]: vlan0: soliciting an IPv6 router
> Sep 16 15:56:25 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce =
is unreachable
> Sep 16 15:56:25 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce =
is reachable again
> Sep 16 15:56:25 logrus dhcpcd[50070]: vlan0: soliciting an IPv6 router
> Sep 16 15:56:57 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce =
is unreachable
> Sep 16 15:56:58 logrus dhcpcd[50070]: vlan0: soliciting an IPv6 router
> Sep 16 15:56:58 logrus dhcpcd[50070]: vlan0: Router Advertisement from =
fe80::3e8a:b0ff:fe3e:4dce
> Sep 16 15:57:32 logrus dhcpcd[50070]: vlan0: fe80::3e8a:b0ff:fe3e:4dce =
is unreachable
> Sep 16 15:57:32 logrus dhcpcd[50070]: vlan0: soliciting an IPv6 router
> Sep 16 15:57:32 logrus dhcpcd[50070]: vlan0: Router Advertisement from =
fe80::3e8a:b0ff:fe3e:4dce
>=20
> During this same time frame, =E2=80=9Croute monitor=E2=80=9D shows:
>=20
> 15:55:53.573 PID    0 delete neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 =
state PROBE lladdr 3c:8a:b0:3e:4d:ce iface vlan0  15:55:54.002 PID    0 =
add/repl neigh fe80::3e8a:b0ff:fe3e:4dce%vlan0 state REACHABLE lladdr =
3c:8a:b0:3e:4d:ce iface vlan0  15:56:25.148 PID    0 delete neigh =
fe80::3e8a:b0ff:fe3e:4dce%vlan0 state PROBE lladdr 3c:8a:b0:3e:4d:ce =
iface vlan0  15:56:25.212 PID    0 add/repl neigh =
fe80::3e8a:b0ff:fe3e:4dce%vlan0 state REACHABLE lladdr 3c:8a:b0:3e:4d:ce =
iface vlan0  15:56:57.406 PID    0 delete neigh =
fe80::3e8a:b0ff:fe3e:4dce%vlan0 state PROBE lladdr 3c:8a:b0:3e:4d:ce =
iface vlan0  15:56:58.967 PID    0 add/repl neigh =
fe80::3e8a:b0ff:fe3e:4dce%vlan0 state REACHABLE lladdr 3c:8a:b0:3e:4d:ce =
iface vlan0  15:57:32.325 PID    0 delete neigh =
fe80::3e8a:b0ff:fe3e:4dce%vlan0 state PROBE lladdr 3c:8a:b0:3e:4d:ce =
iface vlan0  15:57:34.143 PID    0 add/repl neigh =
fe80::3e8a:b0ff:fe3e:4dce%vlan0 state REACHABLE lladdr 3c:8a:b0:3e:4d:ce =
iface vlan0 =20
>=20
> My concern is that this is sending RS=E2=80=99s to my provider far too =
often.
> Can anyone advise if this is normal, and assuming not, what might
> be wrong?
>=20
> Trimmed dhcpcd.conf is:
>=20
> duid
> persistent
> vendorclassid
> option classless_static_routes
> option rapid_commit
> require dhcp_server_identifier
> slaac private
> noipv6rs
> noipv4
> noipv4ll
> allowinterfaces vlan0
> interface vlan0
>  ipv6only
>  ipv6rs
>  ipv6ra_autoconf
>  ia_pd 0/::/56 intnet1/42 intnet2/56
>=20
> Thanks.
>=20
>                        - Chris
>=20





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